1. Field of the Invention
The present invention relates to a vibrating mirror element, and more particularly, it relates to a vibrating mirror element including driving portions.
2. Description of the Background Art
A vibrating mirror element including driving portions is known in general, as disclosed in each of Japanese Patent No. 3956933, Japanese Patent Laying-Open Nos. 2007-312465 and 2007-10823, Japanese Patent No. 3767577, Japanese Patent Laying-Open Nos. 2004-361889 and 2006-293116 and Japanese Patent No. 4092283, for example.
The aforementioned Japanese Patent No. 3956933 discloses a vibrator (vibrating mirror element) including a reflecting mirror portion, a pair of first spring portions having first end portions connected to both sides of the reflecting mirror portion respectively for supporting the reflecting mirror portion in a vibratile manner, a pair of second spring portions connected to second end portions of the pair of first spring portions respectively and each branched into two portions, and driving sources made of a piezoelectric substance arranged on upper portions of the four branched portions of the pair of second spring portions. The pair of first spring portions of the vibrator are torsionally vibratile, while the pair of second spring portions are flexurally vibratile and torsionally vibratile. Thus, vibration from the driving sources is converted to flexural vibration of the pair of second spring portions and the flexural vibration of the pair of second spring portions is converted to torsional vibration of the pair of first spring portions, so that the reflecting mirror portion can change a light reflecting direction. The driving sources arranged on the upper portions of the second spring portions are formed to extend oppositely to the first spring portions and the reflecting mirror portion. Further, the first spring portions and the second spring portions are integrally formed while geometrical moments of inertia of the first spring portions are rendered larger than those of the second spring portions, and hence the width of the first spring portions is conceivably rendered larger than that of the second spring portions receiving the driving sources on the upper portions thereof.
The aforementioned Japanese Patent Laying-Open No. 2007-312465 discloses an optical scanning apparatus including a mirror, a rectangular movable frame provided with support portions having first end portions connected to both sides of the mirror respectively for supporting the mirror and formed on the outer peripheral side of the mirror to surround the mirror, and piezoelectric elements arranged on all of the four sides of the movable frame. In this optical scanning apparatus, the piezoelectric elements are arranged on all of the four sides of the movable frame, so that the movable frame can be displaced without twisting the support portions.
The aforementioned Japanese Patent Laying-Open No. 2007-10823 discloses a driving mirror including a mirror portion, beams having first end portions connected to both sides of the mirror portion respectively for supporting the mirror portion, four arms arranged in pairs to vertically hold the beams therebetween respectively for rotating the beams, and piezoelectric films provided on the four arms respectively.
The aforementioned Japanese Patent No. 3767577 discloses a scanning apparatus including a polariscope (mirror portion), an elastic body whose both end portions are fixed in a state arcuately deflecting an intermediate portion while the polariscope is fixed to a substantially central portion thereof, and driving means consisting of a piezoelectric element fixed onto one end portion of the elastic body.
The aforementioned Japanese Patent Laying-Open No. 2004-361889 discloses a scanning mirror including a rotating mirror and three cantilevers prepared by bonding elastic members and piezoelectric members to each other. In this scanning mirror, free ends of the three cantilevers are arranged above the peripheral portion of the rotating mirror respectively. The scanning mirror is formed to incline the rotating mirror by applying voltages to the three cantilevers respectively thereby vertically moving the free ends of the cantilevers and pressing the peripheral portion of the rotating mirror.
The aforementioned Japanese Patent Laying-Open No. 2006-293116 discloses an optical scanning apparatus (vibrating mirror element) including a mirror portion, a substrate provided with torsion beam portions having first end portions connected to both sides of the mirror portion respectively for supporting the mirror portion, and a piezoelectric body partially arranged on the substrate. In this optical scanning apparatus, the overall substrate vibrates by vibration from the piezoelectric body, whereby the torsion beam portions torsionally vibrate. Thus, the mirror portion is inclined.
The aforementioned Japanese Patent No. 4092283 discloses a two-dimensional optical scanner (vibrating mirror element) including a mirror portion, a pair of torsion bars swingably supporting the mirror portion from both sides, a movable frame, supporting end portions of the pair of torsion bars, formed to surround the mirror portion, forward end driving portions symmetrically arranged to hold the torsion bars therebetween for separately supporting the mirror portion in the vicinity of the pair of torsion bars, and piezoelectric unimorphic diaphragms symmetrically arranged in the vicinity of the forward end driving portions to hold the torsion bars therebetween. This two-dimensional optical scanner is so formed that the forward end driving portion arranged on the side of one of the torsion bars moves downward when the forward end driving portion arranged on the side of the other one of the torsion bars moves upward, thereby inclining the mirror portion and the torsion bars. The piezoelectric unimorphic diaphragms are symmetrically arranged to hold the pair of torsion bars therebetween, and hence the two-dimensional optical scanner is provided with four piezoelectric unimorphic diaphragms in total.
In the vibrator (vibrating mirror element) described in the aforementioned Japanese Patent No. 3956933, however, the width of the first spring portions is rendered larger than that of the second spring portions receiving the driving sources on the upper portions thereof, and hence the first spring portions are disadvantageously hard to deform. When flexural vibration of the second spring portions is converted to torsional vibration of the first spring portions, therefore, torsional vibration of the first spring portions may conceivably be so reduced that inclination and vibration of the reflecting mirror portion are disadvantageously reduced. Further, the driving sources arranged on the upper portions of the second spring portions are formed to extend oppositely to the first spring portions and the reflecting mirror portion, and hence a region occupied by the driving sources, the first spring portions and the reflecting mirror portion is disadvantageously elongated in the extensional direction of the driving sources in plan view. When the vibrator is assembled into an apparatus, therefore, the elongated region may conceivably so restrict the design of the apparatus that it is difficult to downsize the apparatus. Further, a structure for electrically connecting the driving sources with an external device is disadvantageously complicated due to the provision of the four driving sources made of the piezoelectric substance.
The optical scanning apparatus described in the aforementioned Japanese Patent Laying-Open No. 2007-312465 is formed not to twist the support portions, and hence inclination and vibration of the mirror may conceivably be disadvantageously reduced due to suppression of resonance on the support portions. Further, the piezoelectric elements are provided on the four sides of the movable frame respectively, and hence a structure for electrically connecting the piezoelectric elements with an external device is disadvantageously complicated.
In the driving mirror described in the aforementioned Japanese Patent Laying-Open No. 2007-10823, the width of the beams is conceivably rendered substantially identical to that of the four arms provided with the piezoelectric films, and hence the beams may conceivably be disadvantageously hard to deform. Therefore, torsional vibration of the beams may conceivably be so reduced that inclination and vibration of the mirror portion are disadvantageously reduced.
In each of the scanning apparatus and the scanning mirror described in the aforementioned Japanese Patent No. 3767577 and the aforementioned Japanese Patent Laying-Open No. 2004-361889, the piezoelectric element (piezoelectric members) is directly provided on the elastic body (cantilevers), and hence the elastic body (cantilevers) may conceivably be disadvantageously hard to resonate. Therefore, it may conceivably be disadvantageously difficult to enlarge vibration of the polariscope (rotating mirror) due to the difficulty in resonance of the elastic body (cantilevers).
In the optical scanning apparatus described in the aforementioned Japanese Patent Laying-Open No. 2006-293116, the overall substrate must be vibrated, and hence it may conceivably be disadvantageously difficult to enlarge vibration of the mirror portion.
The two-dimensional optical scanner described in the aforementioned Japanese Patent No. 4092283 includes the four piezoelectric unimorphic diaphragms, and hence a structure for electrically connecting the piezoelectric unimorphic diaphragms with an external device is disadvantageously complicated.